To determine the word that differs in primary stress position from the others:

**Question 3:**
- A. **ingredients** (in-GRED-ients) - stress on the second syllable
- B. **vehicles** (VEH-i-cles) - stress on the first syllable
- C. **sidewalks** (SIDE-walks) - stress on the first syllable
- D. **customs** (CUS-toms) - stress on the first syllable

The answer is **A** (ingredients), as it has stress on the second syllable, while the others have stress on the first syllable.

**Question 4:**
- A. **connect** (con-NECT) - stress on the second syllable
- B. **polite** (po-LITE) - stress on the second syllable
- C. **crowded** (CROW-ded) - stress on the first syllable
- D. **avoid** (a-VOID) - stress on the second syllable

The answer is **C** (crowded), as it has stress on the first syllable, while the others have stress on the second syllable.

So, the answers are:
- Question 3: **A**
- Question 4: **C**